TRACON controller reports of operational error due to aircraft slowing more than he thought on final...

Attributes
ACN	1179572
Time
Date	201406
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	Medium Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	Light Transport High Wing 2 Turboprop Eng
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Approach
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 5
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Speed All Types

Narrative:

It was the 1st day that fusion multiple sensor radar was put in use. The perception of speed is skewed with constant updates as opposed to 8 second updates. Aircraft X was on a base leg to runway 28L indicating 230 KTS. Reported the field in sight and was cleared for the visual approach. Aircraft Y was on vectors for the straight in indicating 210 KTS. Aircraft X slowed to 140 KTS once established on the final. By the time I noticed the overtake it was a little too late. I slowed aircraft Y and turned him out; but still lost separation. This was my 1st session working final in fusion mode on the 1st day that fusion was activated. I was having a hard time with the perception of speed and aircraft X's speed reduction was sudden and drastic compared to the normal operations with aircraft X's type aircraft.in my belief fusion radar is not a reliable resource for working final control. The targets jump and in my opinion don't always give an accurate portrayal of the aircraft's position while the aircraft is in a turn. I recommend that single site radar should be allowed to be used for working final control.

Original NASA ASRS Text

Title: TRACON Controller reports of operational error due to aircraft slowing more than he thought on final; causing the Controller to re-sequence the following aircraft. Controller also attributes the loss of separation due to the use of Fusion Radar; which was his first time actually using it.

Narrative: It was the 1st day that fusion multiple sensor radar was put in use. The perception of speed is skewed with constant updates as opposed to 8 second updates. Aircraft X was on a base leg to Runway 28L indicating 230 KTS. Reported the field in sight and was cleared for the visual approach. Aircraft Y was on vectors for the straight in indicating 210 KTS. Aircraft X slowed to 140 KTS once established on the final. By the time I noticed the overtake it was a little too late. I slowed Aircraft Y and turned him out; but still lost separation. This was my 1st session working final in fusion mode on the 1st day that fusion was activated. I was having a hard time with the perception of speed and Aircraft X's speed reduction was sudden and drastic compared to the normal operations with Aircraft X's type aircraft.In my belief fusion radar is not a reliable resource for working final control. The targets jump and in my opinion don't always give an accurate portrayal of the aircraft's position while the aircraft is in a turn. I recommend that single site radar should be allowed to be used for working final control.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

TRACON controller reports of operational error due to aircraft slowing more than he thought on final; causing the controller to re-sequence the following aircraft. Controller also attributes the loss of separation due to the use of fusion radar; which was his first time actually using it.